Bushing terminal guard



May 5, 1970 D. J. COCHRAN BUSHING TERMINAL GUARD 2 Sheets-Sheet 1 FiledMarch 6, 1968 H m m 2 8 0 D L W ATTORNEY y 5, 1970 D. J. COCHRAN3,510,568

BUSHING TERMINAL GUARD Filed March 6, 1968 2 Sheets-Sheet 2 INVENTOR.DONALD J. COCHRAN BY H 8 ATTORNEY United States Patent US. Cl. 1745 8Claims ABSTRACT OF THE DISCLOSURE A product for the protection oftransformers and other electrical equipment from damage due to shortcircuits attributable to squirrels, birds and other animals or objectsthrough provision of a guard or cover that may be selectively engaged oninsulators of different size to protect circuit wires to an elevation ordistance away from any animal or object supporting surface. The guardwhich fits over terminals and wires of an electrical circuit is formedof a high dielectric material, and it provides a skirt that may bechanged to fit insulators of different size. Arc gap openings areprovided at stepped elevations to establish moisture drain ports andelectrical discharge paths for lightning energy when lightning arrestorsare used. A mechanism inclusive of guide elements for machine cuttingare gap slots in a flexible guard is disclosed. An embodiment of theinvention provides a guard formed of a ribbon of semi-rigid dielectricmaterial disposed in a spiral configuration to facilitate installationwithout interruption of power and further providing a weather protectedarc gap and moisture discharge opening that may be selectivelypositioned at an elevation for registration with installed lightningarrestors.

BACKGROUND OF THE INVENTION 'Each year many electric powerinstallations, or even power stations, are damaged by short circuitsthat are attributable to squirrels, birds or other animals or objects.Squirrels often establish a bypass circuit interconnecting a transformercase and the input lead wires. On some installations or where lightningarrestors are used, birds or even small objects have caused seriousdamage to electrical power circuits and equipment. In addition to theinconvenience of a power outage, considerably expense can be involved inre-establshing normal operations. To avoid such problems various typesof wire covers and guards have been used to prevent the short circuitingof electrical components. A type of cover or guard that can be fitted toan electrical insulator to protect the input line for a slight distanceaway from the insulator has been found to be highly advantageous. Amajor problem arises in the field, however, since it has previously beennecessary to provide guards of different size to fit the various sizeinsulators and input wires that are used. A further problem has beenrecognized where lightning arrestors are applied to the electricalcircuit or to the power components that are to be protected. Thedrilling or cutting of an opening in previous squirrel guards that wouldregister with the arc gap points of a lightning arrestor has detractedfrom the in-field acceptance of previous guards. To provide guards ofimproved design and utility, the present inventor herewith presentsseparate embodiments of his invention.

SUMMARY OF THE INVENTION Briefly stated, a first embodiment of theinvention provides a guard or cover for electrical circuits which isformed of a flexible high dielectrical material. A skirt portion of theguard provides internal bead structures that are of a size to beconveniently engaged with insulators 'ice of dilferent size. Provisionis made for fitting the guard to a particular insulator with the beadconstruction engaged to a first convolution of an insulator bushing.When so engaged, the guard will cover and protect a substantial lengthof the input lead wire so that a squirrel or other animal cannotcomplete a bypass circuit between the input wire and other electrical orground components. Being flexible, the guard can be conformed to theshape of the input wire, and provision is made for close engagementbetween the wire and the upper end of the guard to prevent excessiveingress of moisture that may follow down along the wire. A plurality ofopenings are provided at various elevations of the guard. These openingsserve a dual purpose, inasmuch as a lower opening provides an outlet forany moisture accumulated within the cover, and in installations wherelightning arrestors are used the openings further provide a path for alightning are from the input line to the bypass ground wire. Themechanisms and method used for providing the openings in a flexibleguard includes the use of multiple cutting wheels that are brought intocutting engagement with a deformed guard positioned within guideelements of a cutting machine.

A further embodiment of the invention provides a guard that is formed ofa semi-rigid dielectric material. The cover may have a characteristicconical shape, and it will in any instance provide a continuous slot sothat the guard may be introduced onto an already installed power line.When fabricated from a strip of material wound about itself, acontinuous or interrupted slot will be provided at the junction betweenadjacent sections of the strip through which a lightning arc could pass.The actual slot or gap may be provided by notches cut in an edge of thematerial or by spacing one winding of the structural material away fromthe next adjacent winding. As in the previous embodiment, the slot orgap will also prevent the entrapment of moisture within the guard.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view showing a firstembodiment of this invention as installed, with a dotted linerepresentation showing a possible alternate position,

FIG. 2 is a front elevation in partial section showing features of saidfirst embodiment,

FIG. 3 is a side view showing a method and mechanism for cutting slot insaid guard,

FIG. 4 is a top view of such slotting operation and machine,

FIG. 5 is a partial cross-sectional elevation showing the guardpositioned with respect to a lightning arrestor,

FIG. 6 is a side view showing installation of a second embodiment of theinvention,

FIG. 7 is a layout showing further features of construction for thesecond embodiment,

FIG. 8 is a partial elevation showing details of an arc gap slot inenlarger detail,

FIG. 9 is a cross-section taken along the line 99 of FIG. 8, and

FIG. 10 is a cross-section showing a modified type of arc gap preservingconstruction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of theinvention, as shown in FIGS. 1-5, provides a guard 11 of conical form,the top 12 of which may be cut off to provide a top opening 13 whichwill closely receive an input power line 14. The cover 11 has aplurality of internal beads 15, 16, 17 and 18 so that the guard can beapplied directly to the convolutions 19 of an insulator 21. Since allinsulators are not of the same size, it is intended that the guard 11may be cut off at a position just below any of the bead structures 15-18to effectively shorten the guard 11 and to coincidentally reduce thediameter of the bottom of the exposed bead 16-18. Preferably, the guard11 is made of a flexible and elastic material, and, accordingly, withthe proper design the guard can be fitted securely to the topconvolution of various sized insulators 21. Since the guard is flexibleand resilient, it can be bent to alternate shapes as shown in FIG. 1 toconform to the shape of the input wire 14. If care is exercised incutting off the tip 12 of the cover structure, the walls of the guard 11will closely engage the input wire 14 to substantially prevent the introduction of water to the interior of the guard either directly or dueto water that courses down the input wire 14. In order to preventaccumulations of water within the guard 11 that might short out theelectrical circuit, a plurality of openings 22 are provided in the sidewalls of the guard structure. In addition to providing an opening forthe elimination of water and for the ventilation of the guard to preventa moisture buildup Within the device, these same openings provide anadditional benefit, inasmuch as they are purposely positioned toregister with the arc prongs 23 and 24 of lightning arrestors.

As shown in FIG. 5, if the largest bead 15 is engaged with a topconvolution 19 of an insulator 21, an opening 26 that is just above thebead 16 will be in position of alignment with respect to the line prong23 and the ground prong 24 of a lightning arrestor assembly 27 which ismounted on but insulated from the transformer 28. With this arrangementif lightning hits the power lines and is led down the input line 14, anelectrical discharge will be created across the arc prongs 23 and 24 tobe carried to the ground by the lightning arrestor assembly 27. Thisprovision of spaced openings 22 to be registered with lightning arrestorcomponents represents an advantage of the present invention. Inconnection with such installation it should be noted that while anyopening 22 provides an arc path, the main structure of the guard 11 andspecifically the side walls thereof surrounding the openings 22 wouldprevent a squirrel, cat or bird from establishing contact across theprongs 23 and 24 to cause a short circuit of the power line 14. Theconstruction, accordingly, prevents undesirable short circuits whilepermitting the escape of substantial overloads of the type occasioned bylightning bolts.

The provision of these desirable openings 22 creates a special problemin manufacturing. Since the holes are disposed upwardly at a substantialelevation above the initial base 29, it would be difficult to provide apunch anvil of sufficient strength to operate on the interior of theconical guard. This would be especially true at the top where theinterior of the guard is of small cross-section. In the presentembodiment of the invention the desired holes 22 have been cut in theslope face of the guards 11. A mechanism 31 for machine cutting theseopenings in the flexible guard is shown in FIGS. 3 and 4. Here it willbe seen that a motor 32 is connected by a belt 33 to a cutter arbor 34.A plurality of cutters 36 are disposed for rotation with the arbor 34.The motor and arbor are attached to a reciprocally movable frame 37which can be moved with respect to a support frame 38 toward and awayfrom a guide structure 39. The guide 39 provides a slot 41 into whichthe flexible guards 11 may be inserted if they are deformed. Stops 42limit the inward movement of the guards 11 so that only a portion 43 ofthe side face is exposed to be cut. After the slots have been made bythe cutters 36, the frame 37 is retracted until another guard 11 may beinserted and positioned for cutting. The cutters may be of conventionalmill cutter design.

Since the use of a flexible guard material not only facilitates thisopening cutting function but also makes it possible to provide a guardthat may be conformed to various shaped input wires 14, the properchoice of materials is of importance in the practice of this invention.The inventor utilizes a vinyl material which has a high dielectricstrength and which is substantially resistant to atmosphericdeterioration. The guards may be dip formed on a heated mandril.Accordingly, less than the full length of guard could be formed withoutnecessitating a change in mold equipment. A product having a singlebead, such as the bead 18, and a plurality of openings could be made andsold in accordance with this invention.

A separate embodiment of the invention is shown in FIGS. 610. Ingeneral, this embodiment again provides an electrical circuit guard 51that may be applied to insulators 21 of transformers 28 and otherelectric power components. A main feature of the second embodiment ofthe invention is directed to an alternate method of construction so thatthe guard 51 is formed from a single strip of material, such as thestrip 50 shown in FIG. 7. The strip 50 is wound about itself in spiralconfiguration to provide the desired shape. The separate convolutions5360 of the strip 50- are wound one about the other with the upperconvolutions overlapping the lower end in such manner that a slot or gapis provided along the spiral length of the strip 50 so that the guard 51may be introduced about an input wire 14 to be rotated until it iscompletely installed to surround and protect the input wire 14.

In order that most water and moisture will be kept out of the guard 51,the upper layers overlap the lower layers. The same gap or slot 62, asshown in FIG. 9, which separates the inner and outer convolutions 59 and60 not only provides a passage for the introduction of input wire 14,but it also makes it possible to conveniently provide a plurality of arcgaps 63 which may be brought into registration with the prongs 23 and 24of a lightning arrestor assembly 27. When the base 69 is engaged againstthe top convolution 19 of the insulator 21, the guard 51 can, of course,be freely rotated until an arc gap opening 63 is directly aligned withthe prongs 23 and 24 of the lightning arrestor 27 This same form ofspiral wound construction can be used to provide a slightly modifiedform as shown in FIG. 10, in which an upper convolution 71 is spacedfrom a lower convolution 73 by spaced apart raised knobs 74. Thisconstruction will provide a near continuous gap 72 that is interruptedonly by the knobs 74. As before, the continuous type gap 72 can beregistered with the lightning arrestor prongs 23 and 24. If lightninghits, the electrical discharge would tend to follow a slightly curvedpath between the prongs 23 and 24, but this would not be a problem withthe type of voltages that are involved.

In general, the second embodiment of the invention, whether gaps of thetype shown at 63 or 72 are provided, provides an overlapping wound typeconstruction which makes it possible to install a guard on an alreadyconnected input line so that service will not have to be interrupted.This is a highly beneficial feature which contributes to improved fieldacceptance. As in the previous embodiment, a guard 51 of substantiallyconical shape can be cut off at different bottom elevations to provide aguard having a base 69 of a proper size for engagement with differentsized insulators. Similarly, the top 52 can be cut off to accommodatethe guard 51 to wires of different size.

In the construction of guards made in accordance with this secondembodiment of the invention, vinyl, glass reinforced plastics or othermaterials can be used. Fiber reinforced plastic can be [provided thathas a higher dielectric strength and that is less subject to atmosphericdeterioration. The materials used should have a self-extinguishing firecharacteristic. In the construction of a spiral wound type of guard, apre-impregnated glass strip 50 could be used to facilitate fabricationoperations.

The fiber reinforced plastic or other material used in the manufactureof a spiral wound guard 51 should be substantially resilient to permitthe deformation required when the input wire is being inserted. The sameresilience coupled with the long spiral wound construction can make itpossible to provide a single form and size of guard that could besecurely applied to insulators of different size Without any requirementfor cutting off the bottom of the guard. With this construction a bottomof small size could be stretched to fit the guard to larger insula-tors.

I claim:

1. A guard to prevent the short circuiting of electrical components byblocking access to powered wire leads of said components in positionsadjacent input and output insulators, lighting arrestors and othernon-powered elements of said components comprising a hollow body ofvarying sizes along the length thereof, a small end on said body forengagement with the powered wire leads of said electrical components,and a larger end on said body for engagement with non-powered elementsof said electrical components at positions adjacent said leads, saidbody providing a plurality of non-powered element engaging members ofvaried size at spaced positions on said body whereby portions of saidguard at opposite ends thereof may be cut away to adapt said guard foruse with wire leads and non-powered elements of varied size.

2. A guard structure as set forth in claim 1 wherein the guard bodyfurther provides a plurality of openings disposed in position along thelength thereof to provide arc gap paths for lightning arrestors that maybe disposed at various elevations on said electrical components.

3. A guard structure as set forth in claim 1 wherein the guard is ofhollow conical form and wherein said nonpowered element engaging membersare separate bead structures of ring form disposed on an interiorsurface of said hollow conical guard.

4. A guard structure as set forth in claim 1 wherein said guard isformed of a strip of material of tapering width disposed in spiralconfiguration with a slot between adjacent convolutions thereof wherebysaid guard may be installed over in-place lead wires.

5. A guard structure as set forth in claim 4 wherein the guard isintended for near vertical disposition and wherein the edge of thespirally disposed strip of material positioned above a lower convolutionthereof overlaps the edge of said lower convolution to minimize moistureingress through said slot,

6. A guard structure as set forth in claim 5 and further comprisingprotrusions in spaced positions along said convoluted strip of materialfor contact with the next adjacent convolution whereby said slot openingis maintained.

7. A guard structure as set forth in claim 1 wherein said guard isformed of a strip of material disposed in a spiral configuration ofoverall hollow conical shape with a spiral slot disposed betweenadjacent convolutions thereof and wherein said strip of material furtherhas a plurality of notches along an edge of said strip to provide spacedopenings for are gap paths of increased size for use on installationswherein lightning arrestors are applied to said electrical components.

8. The method for providing slot openings in the flexible body of ahollow bushing terminal guard comprising the steps of deforming curvedsurfaces of the body of said guard to increase the curvature thereof,introducing the deformed portion of said body into a confining guide,and subsequently cutting transverse notches in said body across andthrough the deformed face thereof to provide slot openings of increasedwidth having side edges of increased angularity.

References Cited UNITED STATES PATENTS 1,967,014 7/1934 Taverner 174-52,065,315 12/1936 Keath 174-211 X 2,263,319 11/1941 Treanor 174-1392,972,779 2/1961 Cowley 83-17 X 3,019,287 1/1962 Newcomb et al.3,050,842 8/1962 Evans 83-19 X 3,238,291 3/1966 Bosch et al. 3,249,6795/1966 Bogese.

LARAMIE E. ASKIN, Primary Examiner U.S. Cl. X.R.

